We will prepare and fractionate the proteins of human neutrophil polymorphonuclear granulocytes. Antimicrobial proteins will be identified and characterized. The distribution of these proteins in the phagocytes and in the reticuloendothelial system will be investigated and the control of degranulation studied. Methods in use include isopycnic centrifugation, column chromatography, polyacrylamide gel electrophoresis, high performance liquid chromatography, antimicrobial testing, enzyme assay, and immunofluorescence. Experiments will be extended to mononuclear phagocytes and macrophages.